This invention relates generally to a system for connecting a highway truck to a trailer and more particularly to a dolly that provides adjustable weight distribution.
U.S. Pat. No. 4,070,033 to Weir et al. describes a dolly having an inclined frame supported at its lower rear end on running gear. A forward end of the dolly includes a king pin connected to a truck fifth wheel. A second fifth wheel is located on top of the dolly and is repositionable on the inclined frame. The dolly fifth wheel interlocks with a kingpin on the highway trailer. The dolly fifth wheel allows weight of the trailer to be distributed at different locations on the dolly.
The dolly in Weir et al. is difficult to control while the truck is going both in a forward and backward direction. For example, two separate pivot points exist between the truck and dolly (truck fifth wheel) and the dolly and trailer (dolly fifth wheel). The two pivot locations on the dolly both rotate when the truck is navigating around corners making the dolly and trailer difficult to control. The dual pivot points make the dolly and trailer even more difficult to control while the truck is backing up.
The dolly in Weir et al. also has limited adjustability with respect to both weight distribution and extendable wheelbase. For example, to displace more weight on the drive tires of the truck, the slideable king pin must be moved closer to the front end of the dolly. This results in reducing the effective overall wheelbase between the drive wheels on the truck and the tandem wheels on the trailer. Thus, the dolly may not meet state regulations which specify maximum vehicle weight according to interaxle distance.
Accordingly, a need remains for a weight distribution system for highway vehicles that is easy to control while also maintaining increased between the axles of the truck and trailer.